Polymers containing ester groups such as, for example, polyesters, polyester-based polyurethanes, polyester-based polyureas and polyester-based polyamides have less than desirable water-resistance properties due to hydrolysis of the ester group.
In accordance with this invention, it has been found that the water-resistance properties of polyester-based polyurethanes can be remarkably enhanced, without adversely affecting the transparency properties of these materials to any significant degree, by including in the polymer a substantially dispersed nano-particle proton scavenger.
Thus, this invention provides a hydrolytically stable polyurethane nanocomposite comprising a solid polyester-polyurethane polymer containing proton scavenger nanoparticles in a substantially dispersed form.
In addition, this invention further provides a colloidally stable aqueous dispersion comprising water, a polyester-polyurethane polymer and substantially dispersed proton scavenger nanoparticles.
In addition, this invention further provides processes for making such an aqueous dispersion in which these proton scavenger nanoparticles already in a substantially dispersed form are combined with at least one of (a) the prepolymer used to form this polyester-polyurethane polymer before this prepolymer is combined with water for forming an aqueous dispersion, (b) this prepolymer after or during the period it is combined with water forming an aqueous prepolymer dispersion, (c) one or more ingredients forming this prepolymer, (d) an aqueous dispersion of the polyester-polyurethane polymer formed by chain extending this prepolymer, and (e) combinations thereof.
In addition, this invention also provides other processes for making such a dispersion in which a preliminary material comprising the proton scavenger in the form of particles and/or agglomerates having a larger particle size than the substantially dispersed nanoparticles is comminuted in the presence of at least one of (a) the prepolymer used to form this polyester-polyurethane polymer before this prepolymer is combined with water for forming an aqueous dispersion, (b) this prepolymer after or during the period it is combined with water forming an aqueous prepolymer dispersion, (c) one or more ingredients forming this prepolymer, and (d) combinations thereof.